This invention concerns a connector clip and more particularly a dual conductor connector clip adapted for releasable attachment to and removal from a miniature internal combustion engine.
In starting a miniature internal combustion engine a source of electrical current must be temporarily connected to the glow plug of the engine. After the engine has been started and is running, however, the electrical connection is removed and the heat of the running engine alone is sufficient to maintain the glow plug at operating temperature.
The method most commonly used to connect a miniature engine to a current source is to connect the two terminals of a battery to a clip and then to attach this clip to the engine prior to startup. Clips currently in use (such as that disclosed in U.S. Pat. No. 2,928,067), suffer from a number of practical disadvantages which make their use in some cases both dangerous and inefficient.
First among these disadvantages are problems of electrical reliability. Clips of the type disclosed in U.S. Pat. No. 2,928,067, for example, consist of two pivoting contacts; one contact contains a depression which bears on the tip of the glow plug of the engine, while the other contains a flange designed to engage a protruding surface of the engine. The contact which contains the depression presents a relatively small area for electrical contact between it and the tip of the glow plug. Even more significantly, however, the depression itself creates an ideal area for oxidation and the accumulation of dirt and other foreign materials, both of which sharply reduce the effectiveness and reliability of the electrical contact after prolonged use of the clip.
In addition, such pivoting contact type connector clips can present safety problems if not used properly or after prolonged periods of use. During startup the miniature engine generally vibrates severely. In such instances, the glow plug tip can vibrate out of the shallow depression formed in the clip. This allows the clip to slip off of the engine and possibly to fall into the spinning propeller with consequent injury to the operator and damage to the engine.
Finally, such connector clips are commonly constructed with springs which weaken after prolonged use. The purpose of the spring is to provide a holding force securing the connector clip to the miniature engine. When a spring weakens after prolonged use the holding force is reduced, and the connector clip is less securely held to the engine. Electrical reliability problems are made more severe because of reduced contact pressure, and the clip is more likely to vibrate off the engine during startup.
The connector clip which is the subject of the present invention is an improved clip which is not subject to the above-mentioned disadvantages of commonly used prior art connector clips. The connector clip of this invention comprises two conducting strips of metal separated by an insulator body. One conductor engages the engine, the other engages the insulated tip of the glow plug of the engine in a recess formed in the conductor. The two conductors are positioned substantially parallel to one another, and the contacting surfaces of the two conductors are firmly held to the engine itself by means of a spring. This spring forces one conductor to slide parallel to the other, thereby clamping the engine between the contacting surfaces of the two conductors.
Since the connector clip of the present invention employs a recessed contact which surrounds and fits over the top of the glow plug tip, it not only provides greater electrical contact area, but it has a tendency to clean itself after each use, and thus, to minimize the accumulation of dirt and oxidation on the contact. In this way, both the electrical reliability and the performance characteristics of the connector clip of the present invention are improved. Moreover, the recessed contact is designed to lock against the tip of the glow plug, which in combination with the parallel forces exerted by the spring, significantly reduces the chances of the clip accidently vibrating off the engine during startup. In this way, the safety characteristics of the connector clip of the present invention are also improved.